A. Field
Embodiments described herein relate generally to an X-ray diagnosis apparatus and a method for controlling an X-ray irradiation region, and more particularly, to an X-ray diagnosis apparatus and a method for controlling an X-ray irradiation region that can appropriately narrow down an X-ray radiation aperture so as to fit a configuration of a region of interest during acquisition of X-ray projection data for reconstructing tomography images of an object.
B. Background
In recent years, medical image diagnosis by using an X-ray diagnosis apparatus, an X-ray computer tomography (CT) apparatus or a magnetic resonance instrument (MRI) apparatus, has been widely applied for cardiovascular diagnosis and following observation of cardiology in accompany with a development of catheter techniques.
Usually, for performing angiography, two dimensional (2D) or three dimensional (3D) image data is generated by reconstructing X-ray image data acquired through X-ray irradiations over the diagnosis target region along directions more than 180 degrees around the target region. In this case, when some region would have been dropped out from the acquired image, the reconstructed image appears artifacts. To avoid this, for acquiring 2D or 3D images, X-ray irradiations have performed in a wide viewing field so as to sufficiently cover the imaging portion in 180 degrees. As a result, a serious problem of exposure dose on an object has been increased since X-rays are irradiated on an unnecessary portion other than a region of interest in a diagnosis target region.
Generally, an X-ray diagnosis apparatus includes an X-ray generator and an X-ray detector so as to face each other by holding them on a C-arm holder. Further, a collimator is provided between the X-ray generator and the X-ray detector. The collimator includes a plurality of aperture blades for setting up a size and a position of an aperture so that X-rays emitted from the X-ray generator selectively irradiate onto an examination target portion of an object.
A conventional method has been proposed to reduce X-ray exposure dose to an object by moving the aperture blades in an approaching or a seceding direction to or from a center axis of X-ray beams so as to irradiate X-rays onto the diagnosis target region.
The aperture blades in the conventional collimator can be moved merely in an approaching or a seceding directions to or from a center axis of X-ray beams. Accordingly, when a diagnosis target region has a spherical shape, such as a skull bone, having almost equal expanses in every direction, unnecessary X-ray irradiations can be effectively eliminated. However, as illustrated in FIG. 5A, when X-ray irradiations are performed to a diagnosis target region having a strong directionality, such as blood vessels, in the cardiovascular diagnosis, X-rays irradiated onto unnecessary regions of the diagnosis. This causes a serious problem of unnecessary X-ray exposure doses.